Traditionally, thermal silicon oxide (SiO2) films, grown thermally from Si substrates, have been used as gate dielectric films in integrated circuits. More recently, silicon oxynitride (SiON) films have been introduced as the gate dielectric films have become ultra-thin, often only a few atomic layers thick. Incorporation of nitrogen into SiO2 films to form the SiON films has been shown to provide several advantages, including an increase in the dielectric constant (k) of the films and reduced boron penetration through the films. However, as the thickness of the ultra-thin SiON films is further reduced, acceptable leakage currents cannot be maintained.
In order to enable manufacturing of advanced integrated devices, high-dielectric constant (high-k) materials are being implemented as gate dielectric films to replace or supplement SiO2 and SiON films. However, many high-k dielectric materials under evaluation suffer from various problems, such as film crystallization during anneals, growth of interfacial layers during film deposition and further processing, high density of interface traps, reduced channel mobility, reaction with poly-silicon gates, and Fermi level pinning with metal gates. Furthermore, many high-k dielectric materials have dielectric constants that are lower than is desired for many advanced semiconductor devices. Additionally, the dielectric constant of the high-k dielectric materials is lowered by the presence of an interfacial layer formed between the high-k dielectric material and the underlying substrate.
Nitrogen-incorporation into high-k dielectric materials may reduce formation of the interfacial layer between the high-k dielectric material and the underlying substrate and may further reduce dopant penetration into the high-k dielectric material. Nitrogen-incorporation into high-k dielectric materials is commonly performed by post-deposition plasma processing but this can be more difficult than for conventional silicon-based dielectric materials and may cause plasma damage of the high-k dielectric material.
Accordingly, there is a need for further developments for forming high-k dielectric materials to be used in semiconductor devices, such as capacitors and transistors.